Caliber SRT-4 L4-2.4L Turbo VIN F (2007)
Refrigerant Pressure Sensor / Switch: Description and Operation
Operation
OPERATION
The A/C pressure transducer monitors the pressures in the high side of the refrigerant system through its connection to a fitting on the A/C discharge line.
The internal resistance of the A/C pressure transducer changes in response to the pressures it monitors. The totally integrated power module (TIPM)
provides a five volt reference signal and a sensor ground to the A/C pressure transducer. The TIPM then monitors the output voltage of the transducer on
a sensor return circuit to determine refrigerant pressure and sends a message to the powertrain control module (PCM) or the engine control module
(ECM) (depending on engine application) over the CAN C BUS. The PCM/ECM is programmed to respond to this and other sensor inputs by
controlling the operation of the swashplate within the A/C compressor and the radiator cooling fan to help optimize A/C system performance and to
protect the system components from damage. The PCM adjusts the swashplate to nearly a zero degree angle (low compressor displacement) when high
side pressure rises above 3130 kPa (454 psi) and re-adjusts the swashplate to a greater angle (higher compressor displacement) when high side pressure
drops below 1999 kPa (290 psi). The A/C pressure transducer also reduces the swashplate angle if the high side pressure drops below 200 kPa (29 psi)
and will increase the swashplate angle when the high side pressure rises above 234 - 262 kPa (34 - 38 psi). When the refrigerant pressure rises above
1655 kPa (240 psi), the PCM will actuate the cooling fan.
A Schrader-type valve in the A/C discharge line fitting permits the A/C pressure transducer to be removed or installed without disturbing the refrigerant
in the A/C system.
The A/C pressure transducer is diagnosed using a scan tool.
The A/C pressure transducer cannot be adjusted or repaired and must be replaced if found inoperative or damaged.
